That omits what I consider to be a key part of the insight: that the conditions might no longer be able to give rise to new life because today existing organisms would exploit the rich molecules before they had an opportunity to produce proto-living things.
That is very plausible, and it might even be the case that once free oxygen started building up in the atmosphere (from about 2.5 bn years ago, accelerating after 1 bn ya), the environment had become chemically unsuitable.
Another consequence of free oxygen is the formation of an ozone layer, reducing the UV flux at the surface. I guess the significance of that depends on whether UV helped or hindered the process.
Perhaps not in this particular example. Without the oxygen, a bi-product of life, no ozone and no limitation of UV radiation. However other windows of opportunity may have closed. Such as seems to have happened on Mars and Venus.
Note that the oxygen in atmosphere was created by life itself. Oxygen molecules are highly reactive and without a process that continually produces them they would eventually disappear.
"Transparent" is an exaggeration. If the mirror components were abundant, some bacteria would have learn to eat it, and we would have a chiral war. (Perhaps this happened, and we won!)
> These are all L-stereoisomers ("left-handed" isomers), although a few D-amino acids ("right-handed") occur in bacterial envelopes, as a neuromodulator (D-serine), and in some antibiotics.
> Although D-isomers are uncommon in live organisms, gramicidin is a polypeptide made up from mixture of D- and L-amino acids. Other compounds containing D-amino acids are tyrocidine and valinomycin.
Some bacteria can produce the D- version of the amino acids, and use them in peptides that are natural antibiotics because other bacteria don't know how to destroy them. (Anyway, some other bacteria can are resistant, because they developed a way to destroy them.)
Proteins, DNA, and other life structures could be mirrored, but sunlight, minerals, water, and acids can't, and right-handed life has already monopolized them.
This should be easy to observe. If this process of creation of rich-complex molecules is happening today, we should be able to find some of these "ponds" where bacteria feeds on newly created rich molecules. If this found, then we would know why every bit of life on earth today descends from one single common ancestor (Last universal common ancestor)--The more complex of the first lifeforms to exist simply ate every other that arose afterwards.
The efficiency of these reactions is much less than photosynthesis, so don't expect to find this now.
Also, it probably requires an ambient with a lot of methane or some similar compound, but probably other bacteria are eating the methane, or oxygen is destroying it.
>In 2019, researchers in Germany made all four [RNA bases] at once. They placed simple carbon-based chemicals in hot water on a mineral surface and subjected them to repeated wet-dry cycles.
And no one else has been able to do that under other conditions such as undersea vents.
Everywhere the conditions for these processes are met – though it's unlikely it would be going very far on Earth, as this planet is already teeming with bacteria and other life, some of which is certain to find proto-lifeforms delicious.
Not even proto-lifeforms - any pile of interesting organic chemicals is going to immediately be devoured (i.e. go moldy) well before it can spontaneously assemble into anything. This is why we have fridges..
I'm more partial to the idea that a metabolic system to harness energy had to develop before replication and that life started in alkaline hydrothermal vents rather than ponds due to the delivery of energy and concentration of chemicals. Really enjoyed Nick Lane's writing on this topic, highly recommend his books.
The article directly addresses that idea, and suggests it is not a likely answer:
> ...according to a review published in May 2020, “the direct synthesis of amino acids or nucleobases” – both of which are crucial to life as we know it – has “not yet been demonstrated” under alkaline vent conditions.
It does not say that it isn't likely, just that it hasn't been observed. This is the first article on the topic I've seen that even suggest that it isn't strongest candidate.
When I learnt about all the great scientist in school I was always amazed by their brilliance. However I always felt something was missing, what was so different about them that they were able to achieve so much.
Even though I had heard Newton's quote about standing on shoulder of giants I was never able to understand it fully till much later.
All these brilliant discovery had a thread going back to the beginning of our civilization.
It is not just standing on shoulders of giants. It is also that we only hear about the success stories and hardly ever of the long road that lead to the insights and theories. We do this in our era as well which makes it easy to someone as brilliant and think of yourself as not brilliant because you experience your own failures and struggles but only see the successes of others.
> It is also that we only hear about the success stories and hardly ever of the long road that lead to the insights and theories
I have never truly understood a theory until I learned its broken precursors.
One gets a taste of this in physics. Newton to special relativity. (I never got my head around GR.) Or earlier: the different models of atoms, from plum pudding to electron clouds.
It’s a good tool poorly used outside a few examples.
Watching the Cosmos series those giants in their times were like Atlases carrying their work and the social sigma of trying to break dogma. Many of them suffered greatly for us to enjoy the elevated view.
Darwin's generation was around the last who could have a full understanding of all branches of science. Biologists, Physicists, Geologists, Chemists would communicate frequenty through letters and meetings Having that cross-discipline expertise at a high level must have been amazing.
And right now we can have as full an understanding of science at they had without talking to anyone or sifting through private libraries spread through estates across the countries.
And we have a century more of understanding and refinements we can explore should we so desire, all at the press of a button.
They would only dream of the access to science and people we have now. Though twitter would be a poor medium to replace that era's epistolic cross-polination.
Not really no. A single person can no longer know, grok even the whole of biology, or even the whole of molecular biology. Just having a detailed understanding of all the proteins on a mitchondion is a tall order.
Yes, you can look it up. But that's not the same as having an intuitive feel for all of science at the deepest level.
The parents point is that you can identically reproduce the state of knowing what an 18th century polymath knew, today, just by learning a tiny amount of each subject.
Still in the mold of https://hapgood.us/2015/10/17/the-garden-and-the-stream-a-te..., we have accrued tons of "library debt" as we research more things but don't spend commensurately more effort organizing what we've learned. I would not be surprised if this was a huge contributor to the decreasing cost effectiveness of science.
Scientists put a lot of effort in to organizing what we know. Biologists and chemists invest heavily in web databases, and professors love to write books. How do you know that not enough effort is being put in to organization?
Without guidance of some sort, looking it up can be a challenge because you may not know what to search for and vetting new information for quality is its own problem too.
A child on the internet today has to contend with deliberate science misinformation that tries very hard to look valid and authoritative (flat earthers, antivaxxers). This stuff is also likely to intersect with entertainment venues like YouTube and plant their ideas first where you then have to unteach the nonsense just to begin. Even as a science literate adult, navigating this with my children is hard because it brings difficult topics to the table well ahead of their age appropriate academic abilities traditionally prepare them for (religious motivations, philosophy, logic, history, etc).
I'll collapse some additional subthread commentary into a top-level reply:
>Darwin's generation was around the last who could have a full understanding of all branches of science
And
>Not really no. A single person can no longer know, grok even the whole of biology, or even the whole of molecular biology.
have always struck me as odd statements to make.
Not to get pedantic, but that's more of a commentary of our classification of knowledge than the kind of tasks they had to deal with. They were presented with the same living beings that we have today (well, those that aren't extinct anyway). No more, no less.
They had plenty of chances to get overwhelmed with what was in front of them, regardless of what their contemporary science had figured out already.
Put another way, not knowing how things work didn't make their jobs any easier. The way things work doesn't change no matter how many branches of science you throw at it.
> Even though I had heard Newton's quote about standing on shoulder of giants I was never able to understand it fully till much later.
There's an article about this [1] that I enjoyed reading a few years back, titled Standing on the Shoulders of Giants: The Story Behind Newton’s Famous Metaphor for How Knowledge Progresses
150 years ago, 90% of the planet were aboriginals or peasants, 9.9% were workers of some kind, 0.1% were rulers/nobility who were the class that needed to support these ideas, and there were just extremely few people dedicated to knowledge and science.
Rich dudes, their patrons, sitting around pondering the meaning of life.
There was a lot to be discovered and so few people trying to figure it out.
Now we have millions of PhD's studying every little nook and cranny, the vast majority of research ever published will be read by only a small number of people and then forgotten, maybe forever.
The marginal returns to effort now are extremely small.
Edit: 'Professional Scientist' as we understand it is a little bit of a modern concept. Historically it was an interest, not necessarily always profession per sey although I guess by the time of Darwin it was more or less starting to be that [1]
To me beginning of life is a combinatorial issue. You have to have the right combination of lots of different things (chemicals, weather conditions, time etc) to have it happened. What’s scary (or interesting) to me is that we have access to labs and are capable of quickly iterating with lots of different combinations; yet no life arised. If it’s hard in a lab it’s probably a lot harder in nature where to get a different set of combinations you need a new planet! Hence why I think life is rare in the universe.
Take the volume of all the lab experiments ever done, multiplied by the length of time those experiments were run for.
Next take the entire volume of Earth's primordial oceans and multiply by a few hundred million years, roughly the period during which life arose on Earth.
What's the ratio between those two results? The fact that something arose once in the latter tells you very little about what's happening in the former.
I understand your point, but in the lab scenarios we are theoretically using ideal(ish) conditions (or, at least what we think are ideal conditions).
In the random nature scenario, probably 99% of all the instances would be immediately discarded for potential because of 1 or more clearly suboptimal conditions.
Fermi estimate: there have been 10000 experiments of 10L each for a year. That gives 10000L-years. There are ~10^21 liters of water on the Earth. Let’s say life took a billion years to start. 21+9-4=>10^26x.
Let’s say the labs are 99.999999 “efficient” compared to the oceans. That carved off 8 decades, meaning Earth’s experiment was still a million million million times bigger.
But, as the article points out, the size of the oceans may actually work against that by diluting the possibility of getting the correct concentration of ingredients.
Ok so let’s say the conditions only occurred for one day each year, in a one litre puddle. Over just a one hundred million year period. I think that’s an extremely conservative estimate.
Let’s say I have a huge lab and we have 1,000 one litre experiments running continuously. It would still take me 274 years going non stop to recreate the conditions.
Sure, but even if those ideal conditions only existed in a few cubic KM of ocean for a few million years, and life occurred there once, were never going to replicate that.
If it really was likely to happen in a few litres of chemicals over a few years, once those conditions arose in the early oceans we'd expect it to have happened trillions of trillions of times, not just once or a few times.
On the other hand if the conditions were so rare that they only occurred once in a few litres of ocean for a few days, those conditions must be so specific and unusual that we might never figure out how to create them.
But we don’t really even know what’s “ideal”. If you read the article they go through the stages of achievements in laboratory synthesis of amino acids and proteins. Early work focused on heat and electricity. Later work realized that all you need was wet/dry cycles.
You see we’re still figuring out what the conditions should be. Yes we’re good and recreating specific conditions, but we’re still figuring which ones we should strive for.
Natural of course had the luxury of just trying them, in parallel, over vast amounts of time.
You include a good countervailing point in your comment, which is that our experiments are largely confined to what we think are ideal conditions. Evolution (or, whatever you want to call this abiotic Darwinian selective process) searches the space of possible designs randomly, which means it can happen on "improvements" that would be hard to predict a priori.
> Next take the entire volume of Earth's primordial oceans and multiply by a few hundred million years, roughly the period during which life arose on Earth.
Multiplied by more than two to the power of each quantum event of a certain type, if the Everret interpretation of quantum mechanics is true.
If the interpretation is correct, there can indeed be limited interactions between them, or else quantum computing couldn't speed up certain algorithms, so they can indeed have already been observed, but we can't prove it wasn't just through something explained by another interpretation.
But over a billion years or so, vastly more conditions occur on a single planet than we could ever hope to replicate in a lab, and even with the right conditions it might just be unlikely and take a very long time. So I’m still optimistic despite this argument.
Not to detract on your conclusion (I do think like is hard due to some estimates on chemical combinations), but there are way more planets than experiments on Earth about abiogenesis.
Imagine that in each pond several different combinations are being tried in parallel, kind of like in a quantum computer. Of course, the universe is a giant quantum computer. This leads to the idea that even if life is very unlikely, it can still develop since there are so many "attempts". It also means that life can develop many times, but in different attempts. By this I mean different parallel attempts, such that whatever happens in one of these attempts is not accessible to what happens in another attempt.
I also think life is very rare, and I am in fact of the opinion we won't find any other instance of it.
The thing I always struggled with about the "Monkeys at typewriters" type thinking is what about entropy?
Yes with unlimited attempts anything can happen but if you have a force working against it, it could also be equally likely nothing ever happens, it forever remains neutral or not enough time (if a universe has a life span).
The RNA had still to originally come from somewhere.
Big bang produced hydrogen and helium. Primordial stars converted those to heavier elements - carbon, nitrogen... and at some point in time between the first stars exploding and spreading the heavier elements into the universe, and now, the first RNA molecules were formed. What was the chemical process that produced them is the specific question here. Not where in universe this happened. Although that question is exciting as well.
Nothing stops from using Darwin's idea here as well - there was a puddle on a planet, somehwere else, long ago and far away...
Panspermia makes the argument actually more complex, not simpler. But it's not unlikely - space is apparently full of rocks from far away places.
I'm of the same notion, just because the basic combinatorics of various features of even the simplest self-replicating life forms are so exceedingly unlikely that to me the idea that they were developed stochastically in relatively rapid succession in the first billion years on earth just doesn't add up.
It will become clear that I'm no expert, but this has fascinated me a bit and I've seen a few articles about simplest self-replicators. In a lab they've constructed enzymes [1] that are able to do some replication with as few as 160-190 bases of RNA, but they aren't self-replicating, they spew out some subset of themselves.
RNA is just half of DNA with each base in a particular sequence being one of four possible nucleotides (A, C, G and U). In the smallest case above, you have 160 nucleotides giving the entire string of RNA a molar mass of ~ ~50kDa [2] (approximately 50kg per mole of that RNA string). There are ~4^160 combinations of just this extremely short and as far as we know insufficient string of RNA to build even the simplest self-replicator. 4^160 is approximately 2e96 combinations. If you wanted to try every one of those combinations, you would be assembling (2e96 / 6e23) approximately 3e72 moles of RNA. To do it in one shot you would need more mass than in the observable universe (closer to a billion universes). To do it with just the mass of the earth (forget surface/hydrocarbons/biomass) in four billion years you'd have to recycle at relativistic speeds.
Obviously it happened, and the above 'needle in a haystack' assessment has many problems as well. But the numbers are so big that no matter how you slice it I can see a scenario where it plausibly only happened once in the history of the universe. Either that or the stochastic parts of the explanation of abiogenesis are incomplete.
I think Panspermia could explain why it's so hard to reproduce the first organisms in a lab by mimicking Earth's early conditions - we could be using the wrong conditions altogether. E.g. we could be ignoring the effect of solar radiation from another atmosphere, or very high/low atmospheric pressure, etc.
I mean it could also have taken a really long time, right? like the correct conditions could have existed for tens of thousands of years or more before the chance collisions occurred which resulted in self-replicating life.
> why that’s more likely than life developing on Earth?
Possibly because the Universe is much older than our planet, and life could have been evolving out there for billions of years before Earth even existed.
Of course he considered it a theory.[1] It was a new idea. He had a pile of evidence for it (yes, empirical evidence) but it still needed to be looked at by other scientists and the evidence assessed.
I don't know what you mean by "not empirical", but if you mean that Darwin just wrote "hey, here's a cool idea" and didn't have empirical evidence for it then you're just flatly wrong. If you mean that now we don't have empirical evidence for it then either you've been terribly deceived by others or you're lying. (Probably the former. My condolences.)
Something can be a theory and also factual. And there can be a theory of something that is a fact. If you think "X is a theory!" is some sort of refutation of people who regard X as true, then you are 100% wrong about that.
The usual progression goes like this. Someone comes up with a theory (in the vernacular sense). Say, Darwin's theory of how living things got to be the way they are. Some theories are more or less correct from the outset. Some are just plain wrong. Most are somewhere in between. If the theory seems worth taking seriously, other people try to work out its consequences in more detail, and go looking for evidence for or against it, and refine the details. When the theory is all wrong, it will hopefully get knocked down as this happens. (Examples: "cold fusion", Lamarckian "inheritence of acquired characteristics".) When the theory is basically right, the wrong bits will get corrected (e.g., Darwin expected inheritance to be a sort of "mixing" process, which isn't really right and produces some wrong intuitions) and new ideas will be brought in (e.g., Darwin didn't know about genes), and as repeated investigation doesn't refute the underlying ideas it becomes increasingly implausible to reject them.
Today's understanding of evolution isn't identical to Darwin's. He made some mistakes and some wrong guesses and there was a lot he didn't know. But we have a lot more evidence than Darwin did that populations of living things evolve over time, that a major cause of the change they undergo is natural selection, that even very different-looking living things have common ancestors, etc.
Darwin had a "theory" in the vernacular sense: an idea that seemed to explain a lot of things and might or might not turn out to be right. It was a good enough idea that scientists after Darwin put a lot of effort into investigating and refining it. We now have a "theory" in the "grand scientific edifice" sense, and while details will continue -- ahahaha -- evolving, there's little scope for reasonable people aware of the evidence to doubt that its central ideas are facts.
[1] Even in the "vernacular" sense. It's true that sometimes "theory" means "grand scientific edifice, well evidenced and elaborated with mathematical sophistication", but it doesn't always, and when Darwin called evolution by natural selection a "theory" he didn't mean that.
A theory is the pinnacle of scientific achievement - a complete series of observations, equations, processes etc. that come together to describe a phenomenon.
There is nothing that we know with a higher degree of certainty then a scientific theory, such as the theory of evolution, the theory of general relativity, the theory of quantum mechanics, the theory of newtonian mechanics etc.
> The meaning of the term scientific theory (often contracted to theory for brevity) as used in the disciplines of science is significantly different from the common vernacular usage of theory.[4][note 1] In everyday speech, theory can imply an explanation that represents an unsubstantiated and speculative guess,[4] whereas in science it describes an explanation that has been tested and widely accepted as valid. These different usages are comparable to the opposing usages of prediction in science versus common speech, where it denotes a mere hope.
Please take a minute to consider this and realize that you should never repeat what you just said.
What I think it means is irrelevant. It only matters what Darwin thought it meant. You are not inside the head of a person who lived generations ago and loved Victorian novels.
Why should it matter what Darwin thought of it, given that the theory has underwent much further development and ratiocination since his time? The only people who see the theory as solely his intellectual property are creationists.
"There is a notable difference between the opinion of scientists and that of the general public in the United States. A 2009 poll by Pew Research Center found that "Nearly all scientists (97%) say humans and other living things have evolved over time – 87% say evolution is due to natural processes, such as natural selection. The dominant position among scientists – that living things have evolved due to natural processes – is shared by only about a third (32%) of the public."
Um, that's how science works. It's an effort to explain the world. Everything is a theory, nothing is final. Some theories (evolution, gravity) are more credible/developed than others.
> Darwin was proposing that life began, not in the open ocean, but in a smaller body of water on land, which was rich in chemicals